1. Field of the Invention
The present invention relates to a radio selective calling system, and in particular to a selective call receiver having a display for displaying a message on screen.
2. Description of the Related Art
A portable selective call receiver is widely used as a receiving terminal of a radio selective calling system or a paging system. In cases where a call is initiated by using a public telephone switching network, the caller dials a calling number and then transmits an encoded message according to an instruction received from an exchange.
Recently, a paging receiver with such a message transmission function has been proposed (for instance, see Japanese Patent Laid-open Publication No. 2-82824). This kind of receiver is provided with a transmitter and a memory storing a plurality of fixed sentence codes, character codes, and numeral codes. These codes are used by a user to produce a transmission message.
However, the conventional paging receiver cannot edit messages including graphic images but can only edit characters and numerals. It is apparent that graphic images are an important factor in passing information to a person smoothly especially in the case of a paging receiver having a limited display area.
Another paging system which is able to transmit graphic images is disclosed in Japanese Patent Laid-open Publication No. 5-235832. A transmitting side of this system is provided with a memory storing fixed sentence codes and another memory storing image data. By combining fixed sentence codes and image data, a long transmission message can be transmitted.
However, this paging system is intended for use in a large-scale system like a personal computer on the transmitting side. Such a large system cannot be applied to the paging receiver. In addition, since only a single image pattern which is previously registered is transmitted for each calling signal, it is necessary to repeatedly transmit a transmission message in the case of transmitting a plurality of images combined into one. This results remarkably reduced transmission efficiency.